1. Technical Field
This invention generally relates to pusher furnaces. More particularly, the invention relates to a method and apparatus for controlling the position of the sections of a pusher furnace in response to changes in temperature. Specifically, the invention relates to a compression system which engages at least one furnace section and applies pressure thereto to maintain contact between adjacent furnace sections in the pusher furnace.
2. Background Information
Pusher furnaces are designed in various lengths and may contain multiple heating and cooling sections as required by the application. These furnaces include a substantially continuous flat surface or a pair of slide rails running through the interior of the furnace. A plurality of pusher plates, carrying the material to be processed on their upper surfaces, are pushed sequentially along the flat surface and through the heating sections. Materials processed in this manner may include various materials required for electronic or ceramic components, as well as different metals that are to be annealed, sintered or de-waxed. In order to process a particular material properly, that material typically has to be subjected to very specific temperatures and atmospheric conditions as it passes through the furnace.
When the individual heating sections are heated, the overall length of the longitudinally extending furnace increases, sometimes by as much as several inches. Each heating section may be heated to a different temperature and consequently adjacent heating sections will likely expand to differing degrees. Furthermore, if the pusher furnace needs to be shut down in an emergency situation, for example, the various heating sections will tend to cool down at differing rates and, consequently, the heating sections may shrink to differing degrees. This difference in cooling rates can result in adjacent heating sections pulling apart from each other as they contract, thus creating gaps between the adjacent heating sections. Heat and gasses escape through these gaps, potentially causing damage to insulation within the sections and even potentially increasing the risk of catastrophic explosions. Even if the escaping heat and gasses do not cause explosions, they do cause a sudden change in the thermal and atmospheric conditions within the adjacent heating sections and thereby likely lead to damage of the materials being processed.
There is therefore a need in the art for a method and apparatus for keeping the heating sections in a pusher furnace substantially in contact with each other, thereby maintaining the temperature gradients over the entire length of the longitudinally extending furnace.